1. Field of the Invention
The present invention is directed to a support plate for holding sensors, such as a transducer and a tocodynamometer, in selected relationship against the body of a patient.
2. Description of the Related Art
The present invention relates to apparatus for monitoring uterine contractions during pregnancy and throughout labor and delivery and an apparatus for ultrasound monitoring of a mother and the fetus. Information relating to the frequency, magnitude and pattern of uterine contractions is valuable to the physician, as a measure of the normal progression of labor. Additionally, it provides a guide for nurses and physicians in the use of medication or the need for other remedial actions.
The two types of apparatus most widely used at the present time for monitoring labor contractions are: (1) internal catheters inserted into the uterus to measure changes in the amniotic fluid pressure in the amniotic sac such as generally shown in U.S. Pat. No. 4,543,965 to Pack; and (2) external devices which consist of a pressure transducer held in place on the abdomen of the patient by a belt fitted around the waist of the patient such as generally shown in the U.S. Pat. No. 3,520,294 to Fuzzell, and external devices in which the pressure transducer is bound by a strong adhesive on the abdomen of the patient, such as disclosed in U.S. Pat. No. 5,070,888 to Hon et al.
The most reliable device for measuring uterine contractions is an internal type as it usually provides accurate data, but has a number of significant disadvantages which include:
1. The uterine cervix must be partially dilated and the amniotic sac ruptured.
2. During insertion of the catheter, bacterial and/or viral contaminants may be carried from the vagina and/or cervix into the uterine cavity and cause serious infection.
3. The catheter system may not be used where certain complications exist, e.g. uterine bleeding, here catheter insertion might cause additional bleeding; fever due to suspected uterine infection, in this case catheter insertion might exacerbate the situation.
4. If great care is not taken, during insertion of the catheter through its guiding tube, the lower segment of the uterus may be perforated.
5. Catheter insertion is uncomfortable for the patient and inconvenient and time consuming for the medical and nursing staff. Before insertion, a sterile area must be prepared around the vaginal orifice and then draped with sterile towels. The catheter, catheter guide, fluid filled syringe and pressure measuring apparatus then have to be assembled. The entire operation usually takes 7-10 minutes.
6. Even though great care is exercised during catheter insertion, it is possible for the catheter to become clogged with a blood clot or vernix caseosa during labor so that the recorded uterine contraction data is compromised, sometimes to the point where it is not usable, even though the catheter system has been flushed with sterile water. In this case, the catheter must be replaced and the entire insertion process repeated.
7. During attempted flushing it is possible to damage the expensive pressure transducer if the flushing fluid is inadvertently directed towards the pressure transducer rather than towards the catheter.
8. Uterine contractions are often not monitored in the delivery room because current catheter systems usually place the pressure transducer directly on the fetal monitor so that patient transfer from labor to delivery room requires the reconnection of the catheter system to another pressure transducer on another fetal monitor--an awkward and time-consuming process. Additionally, it is difficult to maintain catheter sterility during the transfer process.
One of the external types of apparatus presently used consists of a pressure transducer held in place against the patient's abdomen by an encircling belt without any other fixation means. The belt provides the counter-pressure which keeps the pressure transducer firmly against the maternal abdominal wall during contractions. Without it, the pressure transducer would merely ride up and down with each uterine contraction and hence would not reflect the changes in abdominal wall tension associated with uterine contractions.
While the external system using only an encircling belt to secure the transducer is simple and convenient to use and does not suffer from some of the major disadvantages of the internal system, it too has significant problems, which include:
1. Even under the best of conditions the overall quality of data obtained by external means secured only by a belt is not as precise as that obtained using an internal uterine catheter.
2. Uterine contraction data is easily compromised by fluctuations in belt tension which does not provide the necessary fixation forces to keep the transducer in a fixed relationship to the abdomen. If the labor is intense and the patient moves, belt tension changes continually. Hence for satisfactory operation, the patient must be kept relatively immobile. Once belt tension has been altered by patient movement, the belt tension must be readjusted, otherwise no uterine activity data will be recovered.
3. When the patient is transferred from the labor ward to the delivery room the belt tension has to be readjusted. Because this can be time consuming, it is not usually done so that the external technique is infrequently used in the delivery room.
4. Because of the foregoing problems, such external uterine activity monitoring techniques provide at the best a fragmentary record of uterine activity, even so, much of the data is of poor quality.
The second type of external system in which the transducer assembly is bonded directly onto the abdominal wall of the patient eliminates the fixation problems of the belt system, but was problematic because the removal of the transducer assembly was difficult and required the use of solvents to break the bond to the skin of the patient
U.S. Pat. No. 5,070,888 to Hon et al. teaches the use of a strong adhesive on the abdomen of a patient that formed a solid bond with the skin in order to secure the transducer to the patient. Such an adhesive was sufficiently strong to maintain the transducer in place on the patient without the use of a belt. However, such a system was difficult to remove because the adhesive would bond to the skin of the patient and required the use of solvents for the removal of the transducer from the patient.
In the past, additional means other than a belt for fixing the external transducer to the patient's abdomen or bonding the external transducer to the skin of the patient have been attempted.
As long ago as 1932, in "Surgery, Gynecology and obstetrics," Vol. 55 (1932) at page 45, a tripod support assembly was disclosed which had an air transducer supported in a tripod-like structure which was fixed by tapes tied in ringlets of the tripod which was held fast by adhesive straps to a patient's loins. This structure was not widely employed and is not presently being used. In effect, this system conceptually was a precursor of the belt system.
Another prior art device disclosed in "Science 1947" at page 427 (shown diagrammatically in FIG. 6 thereof) consisted of a heavy brass ring (240 grams) held in place on the abdomen by double coated Scotch brand adhesive tape applied to the bottom side. A strain gauge was held in the center of each ring by a single lever system. This system was devised by Dr. Reynolds, but has never been widely used and is not in use at the present time.
The Reynolds device used doubled-sided adhesive tape to prevent lateral movement of the rings. The weight of the rings provided counter-pressure to hold the strain gauge against the abdomen during episodic changes in abdominal wall tension which occurs with uterine contractions. Since the operation of the device depended on gravitational forces to hold the strain gauge in correct relationship to the abdominal wall, it was mandatory that the patient be on her back and be relatively immobile during the use of the device.
There are a number of medical tests that require the monitoring of a patient, and in particular the monitoring of a mother and the fetus during pregnancy, with an ultrasound transducer, e.g. obtaining the fetal heartbeat, as well as a number of other conditions that cannot be observed directly. In use, a coupling gel is applied to the ultrasound transducer face and the ultrasound transducer is then moved over the area of the patient where the best data is obtained. The data is typically observed on a monitor, and/or is stored on hard storage media.
If data is to be obtained over a long period of time, some means of holding the ultrasound transducer in place is required. The transducer would need to be coupled in a fixed position with respect to the patient and the application of a counterforce to the transducer would be necessary to reflect changes in the abdominal wall tension associated with uterine contractions.
In the past, the means for holding an ultrasound transducer on a patient was accomplished by using an encircling abdominal belt, as is commonly used for holding a tocodynamometer in place during the measurement of contractions in order to provide the necessary counterforce on the transducer. However, such belts when used with an ultrasound transducer are difficult to keep in place because the transducer is not fixed to the patient. To function properly, the ultrasound transducer must be held in a fixed position once the belt has been tightened and locked. Since the surface of the maternal abdomen is not uniform or flat, it is sometimes difficult to fix the orientation of the ultrasound transducer at the optimum angle to obtain the fetal heartbeat. Because the tension of the belt system holds the transducer face essentially parallel to the maternal abdomen wall, it is sometimes difficult to obtain the required data, and it becomes necessary to change this parallel orientation by angulating the transducer face.
Further, the abdomen of the pregnant woman does not maintain a constant shape during the testing period. The movement of the fetus, as well as contractions, cause the shape of the abdomen to change. This change in shape of the abdomen alters the pressure on the belt, causing the belt to slip and change position, thereby also causing the ultrasound transducer to change its position. The required data is thus frequently lost or its reliability is compromised. The instability of a belt system demands constant checking by the nursing and medical staff to make sure that the ultrasound transducer has not moved significantly. Therefore, the use of a belt alone was not satisfactory for securing an ultrasound transducer to the abdomen of a patient because the belt could not provide the necessary fixation forces to fix the position of the transducer with respect to the patient.
In U.S. Pat. No. 4,920,966 to Hon et al., an adhesive layer was applied to the surface of a disc-shaped transducer base in contact with the skin. The adhesive formed a solid bond with the skin in order to secure the transducer to the patient. Such an adhesive was sufficiently strong to maintain the transducer in place on the patient without the use of a belt. However, such a system was difficult to remove because the adhesive would bond to the skin of the patient and required the use of solvents for the removal of the transducer from the patient.
Currently, tocodynamometer recording of uterine conditions is done with a belt enveloping the maternal abdominal wall to hold the tocotransducer in place. Unfortunately, the roughly cylindrical nature of the maternal anatomy coupled with patient movements makes it difficult to obtain satisfactory uterine activity records, especially in late labor.
Therefore, there exists a need for a transducer holder in which the proper fixation and counterforces can be applied to the transducer that is simple to attach and remove from the patient.